In the case where PWM signals are supplied to electric loads such as two electric motors, a high frequency ripple becomes large when energization periods for the loads overlap with each other.
For solving this problem, for example, as disclosed in JP 6-189593A or IP 2002-43910A, two PMW signals are so output as to have a relationship of reverse phase so that the energization periods of those two loads do not overlap with each other. However, the ripple of a supply current can be suppressed only when the duty ratio of the PWM signal is 50%. For example, when a supply voltage is 12 V, only the voltage of 6V that is ½ of the full supply voltage (12 V) can be applied to the respective loads. Accordingly, the drive control range of the loads is limited.